Before claiming any success for any measure in predicting injury, we must fundamentally recognize that any PAP-style metric will be positively correlated with raw pitch counts. Pitchers with high pitch count totals will tend to have high PAP totals. If a PAP function provides no additional insight into which pitchers will be injured that pitch count totals alone, there is no reason to add the added complexity of a PAP system to our sabermetric arsenal.

There are two related effects we are interested in studying. The original intent of PAP was to ascertain whether a pitcher is at risk of injury or permanent reduction in effectiveness due to repeated overwork. And in particular, does PAP (or any similar formula) provide more insight into that risk that simple pitch counts alone?

This week's question comes from Robert Shore, who asks:
Like many people, I was mightily impressed by Voros McCracken's work, which strongly suggested that pitchers have essentially no effect on the conversion of balls in play to outs. It occurred to me to wonder about the converse question. Are some batters better than others in converting balls in play to base hits?

Starting today, we will be periodically running some of the best content from the new, super-charged Baseball Prospectus archives. Those new to BP may be reading this content for the first time. Long-time readers can rekindle old debates. We begin today with Keith Woolner's look at the conversion of balls in play into outs, from 2002. To do your own mining, go to BP's Search function. To request a specific article from the archives, e-mail jkeri@baseballprospectus.com.

There's some merit to the argument that a few starts can skew a pitcher's cumulative line, and there have been attempts, such as
Michael Wolverton's Support-Neutral statistics to better model the maximum impact a single game can have on a pitcher's value.